kasan: remove kasan_find_vm_area() to prevent possible deadlock

find_vm_area() couldn't be called in atomic_context.  If find_vm_area() is
called to reports vm area information, kasan can trigger deadlock like:

CPU0                                CPU1
vmalloc();
 alloc_vmap_area();
  spin_lock(&vn->busy.lock)
                                    spin_lock_bh(&some_lock);
   <interrupt occurs>
   <in softirq>
   spin_lock(&some_lock);
                                    <access invalid address>
                                    kasan_report();
                                     print_report();
                                      print_address_description();
                                       kasan_find_vm_area();
                                        find_vm_area();
                                         spin_lock(&vn->busy.lock) // deadlock!

To prevent possible deadlock while kasan reports, remove kasan_find_vm_area().

Link: https://lkml.kernel.org/r/[email protected]
Fixes: c056a36 ("kasan: print virtual mapping info in reports")
Signed-off-by: Yeoreum Yun <[email protected]>
Reported-by: Yunseong Kim <[email protected]>
Reviewed-by: Andrey Ryabinin <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Dmitriy Vyukov <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: LeviYeoReum

mm/kasan/report.c

@@ -370,36 +370,6 @@ static inline bool init_task_stack_addr(const void *addr)
 			sizeof(init_thread_union.stack));
 }
 
-/*
- * This function is invoked with report_lock (a raw_spinlock) held. A
- * PREEMPT_RT kernel cannot call find_vm_area() as it will acquire a sleeping
- * rt_spinlock.
- *
- * For !RT kernel, the PROVE_RAW_LOCK_NESTING config option will print a
- * lockdep warning for this raw_spinlock -> spinlock dependency. This config
- * option is enabled by default to ensure better test coverage to expose this
- * kind of RT kernel problem. This lockdep splat, however, can be suppressed
- * by using DEFINE_WAIT_OVERRIDE_MAP() if it serves a useful purpose and the
- * invalid PREEMPT_RT case has been taken care of.
- */
-static inline struct vm_struct *kasan_find_vm_area(void *addr)
-{
-	static DEFINE_WAIT_OVERRIDE_MAP(vmalloc_map, LD_WAIT_SLEEP);
-	struct vm_struct *va;
-
-	if (IS_ENABLED(CONFIG_PREEMPT_RT))
-		return NULL;
-
-	/*
-	 * Suppress lockdep warning and fetch vmalloc area of the
-	 * offending address.
-	 */
-	lock_map_acquire_try(&vmalloc_map);
-	va = find_vm_area(addr);
-	lock_map_release(&vmalloc_map);
-	return va;
-}
-
 static void print_address_description(void *addr, u8 tag,
 				      struct kasan_report_info *info)
 {
@@ -429,19 +399,8 @@ static void print_address_description(void *addr, u8 tag,
 	}
 
 	if (is_vmalloc_addr(addr)) {
-		struct vm_struct *va = kasan_find_vm_area(addr);
-
-		if (va) {
-			pr_err("The buggy address belongs to the virtual mapping at\n"
-			       " [%px, %px) created by:\n"
-			       " %pS\n",
-			       va->addr, va->addr + va->size, va->caller);
-			pr_err("\n");
-
-			page = vmalloc_to_page(addr);
-		} else {
-			pr_err("The buggy address %px belongs to a vmalloc virtual mapping\n", addr);
-		}
+		pr_err("The buggy address %px belongs to a vmalloc virtual mapping\n", addr);
+		page = vmalloc_to_page(addr);
 	}
 
 	if (page) {